Naphthalenic compounds as termite bait toxicants

ABSTRACT

Termite foods mixed together in a matrix suitable to be used as baits and attractants for termites are provided. They comprise cellulose, naphthalenic compounds, water and potentially other termite-preferred nutrients. Methods of monitoring the presence of termites using such matrices and methods of controlling termites using such matrices to deliver termite toxins are also provided.

BACKGROUND OF THE INVENTION

This invention relates to use of naphthalenic compounds as effectivebait toxicants for their use in the control of termites.

Damage in the United States attributable to subterranean termites is nowestimated to be in excess of one billion dollars a year. All wooden orwood-containing structures are potentially affected, including homes,outbuildings, fences, utility poles, railway sleepers, boats, bridges,retaining walls and even living trees. Since their introduction to theUnited States within the last half-century, Formosan subterraneantermites (FST), Coptotermes formosanus (Shiraki), have become one of themost destructive pests in the contiguous United States. Reasons for thisinclude their massive colonies which can contain tens of millions ofindividuals, their ability to attack several species of living trees,and their high level of reproduction.

The most successful existing methods for control of subterraneantermites are preventive rather than remedial. These include barriertreatments to structures and the pre-emptive treatment of wood materialswith chemicals to prevent termite attack. These methods, however, havedrawbacks. Physical barriers are not compatible for retrofitting on manyexisting constructions and may not be completely effective, and chemicaltreatments are only partially effective and last only about five years.

Low toxicity baits utilizing growth regulators have shown success inreducing damage caused by subterranean termites, with diflubenzuron andhexaflumuron having been particularly effective in suppressing coloniesof C. formosanus and Reticulitermes spp. Bait matrices utilized for thebaits have consisted of cardboard, filter paper, pine wood, purecellulose, and recently the use of a nutritionally based matrix.Depending on the species of termite, these matrices have shown to beeffective toxicant carriers. Chen et al. (Naphthalene in FormosanTermite Carton Nests; Journal Agricultural Food Chemistry, Vol. 46, No.6, 1998) disclose the presence of naphthalene in termite carton nestsand postulated that it might constitute a unique chemical defensestrategy for Formosan termites. Grace et al. (Evaluation of the TermiteResistance of Wood Pressure Treated with Copper Naphthenate; ForestProducts Journal, Vol. 43, No. 11/12, November/December 1993) teachesthat copper naphthenate is not only toxic to termites but is also highlyrepellent to them.

While various methodologies and compositions exist for the monitoringand control of termites, there remains a need for the creation ofimproved tools in this area.

Therefore, it is an object of this invention to provide alternativecompounds as bait active ingredients effective as toxicants fortermites.

Yet another object is to provide compositions and methods for theeffective control of termite populations.

SUMMARY OF THE INVENTION

We have discovered that termites may be more effectively controlledthrough use of naphthalenic compounds in matrices at fairly lowconcentrations. These compounds work as an attractant for chemicalsystems which are toxic to termites. A termite matrix containingnutritionally requisite components enhances its usefulness as a bait andan aggregant for termites. The invention is premised on Applicants'discovery that termites aggregate and feed on food sources that containnaphthalenic compounds.

Termites for which the naphthalene and naphthalene derivatives of thisinvention are useful include all termite species belonging to thefamilies Rhinotermitidae and Kalotermitidae, preferably Coptotermesformosanus, Reticulitermes flavipes (Kollar) and Reticulitermesvirginicus.

The nutritionally based matrix may also be used as a highly effectivecarrier for enhancing the delivery of these termite toxicants for thepurpose of destroying substantial numbers of termites and thusinhibiting termite damage to cellulosic structures such as buildings andtrees.

Methods of making termite-preferred matrices of this invention are alsoprovided comprising mixing the various components to form a toxicantcontaining food.

Methods of killing termites are also provided comprising placing atoxin-containing matrix in a termite habitat upon which the termiteswill preferentially feed in place of other environmentally-availablefood sources. The methods preferably also include placing hydrated,water-retaining materials, also referred to herein as water-retentionagents, within the termite bait matrix or in the area immediatelysurrounding the termite matrix to provide a degree of humidity to theimmediate area which can be detected by termites to serve as a secondmeans of attracting them.

A termite aggregant comprising a hydrated water-retention agentcontained within a termite-accessible container is also provided. Thetermite-accessible container refers to a container or coating whichretains moisture inside but which termites can enter.

DETAILED DESCRIPTION

Naphthalenic compounds incorporated into cellulose-based matrices forthe control of termites have been developed. Low concentrations of thesechemicals are sufficient to kill native and Formosan termites coloniesin field conditions. Naphthalenic compounds are considered to be any ofthose that possess a base structure of naphthalene. These chemicals canbe used in baiting systems as a novel approach to reduce the amount oftoxins required to kill termites. The matrix composition comprisescellulose, water, and naphthalene derivatives and termite-preferrednutrients.

The cellulose may be supplied by means of any cellulose-containingmaterial, preferably having at least 50% to greater than 95% cellulose,so long as it does not include chemicals which are repellant totermites. Such usable materials include commercially availablecellulose, wood, paper, and cardboard, and are preferably in particulateform for ease of mixing with the other ingredients of the matrix.Sawdust may be used from any plant source but is preferably from woodspreferred by termites such as aspen, sitka spruce, maple, birch, sweetgum and related woods or any such species possessing a low content offeeding deterrent chemicals as determinable by means well known in theart. Alternate sources of sawdust, while usable, may contain chemicalsin amounts that reduce the utility of such sawdust materials due toeither repellant or toxic effects.

The degree to which the presence of a particular component causestermites to prefer a food over other foods not containing the component,or containing greater or lesser amounts thereof, may readily be assessedusing methods known in the art.

The matrix further comprises naphthalenic compounds present in amountsranging from about 10 ppm to about 500 ppm. Usable compounds are seen toinclude N-hydroxynaphthalimide (NHA), 1,8-napthalimide and sodium,magnesium, potassium and calcium salts thereof and copper naphthenateand zinc naphthenate.

Subterranean termites prefer moist foods. To be more attractive thanother available foods in the environment, the formulation of thisinvention should be preferably moist. Enough water should be used toallow mixing of the matrix material, and/or completely hydrate theparticulate or solid cellulose materials and to provide excess water tomaintain a humid environment. In general about three-fourths by weightof the matrix should be water, but this may vary with the water contentranging from about 20% to about 90% by weight of the composition.

A water-retention agent capable of absorbing water and releasing itslowly to the environment can be used to ensure an acceptable moisturelevel in the matrix material as well as to serve as another means fortermite aggregation. Examples of such materials include agar andpolyacrylamide, but may include any substance not otherwise possessing arepellant effect. Examples of preferred usable materials include thepolyacrylamide graft copolymer such as Terrawet® T-400 Aquawet (TerrawetCompany, San Diego, Calif.), which can absorb and retain up to athousand times their own weight in water. These materials should behydrated, preferably fully-hydrated, with the addition of at leastthirty times their weight in water containing the water-solublenaphthalene derivatives, such as NHA. The hydrated water-retainingmaterials may be mixed with the matrix.

The inventors have discovered that termites are attracted during theirforaging to high humidity conditions, preferably at least about 80%humidity, and more preferably at least about 90% humidity. Thus,moisture-retaining material as described above is preferably placed inthe immediate environment of the bait matrix to provide a humidityreadily detectable by, and attractive to, termites. In a preferredembodiment in which a polyacrylamide graft copolymer such as Terrawet®400 Aquawet is used as the water-retaining agent, it may be placed inthe area of a termite bait or monitoring station at an application rateeffective for eliciting an aggregant response, that is, from about 1 gto about 10 g (dry weight) per square foot. The hydrated-polyacrylamide,preferably hydrated to a NHA-water: polymer weight ratio of at leastabout 30:1, with a final concentration of NHA of 900 ppm, can beinjected into the soil around the bait station by pressure usingcommercially available injectors, preferably to a radius around the baitmatrix of at least about 2.5 cm, or placing it on the base of thestation or inside of the above ground station or in the cracks of wallsand trees or other locations susceptible to termite infestation. Otherwater-retaining agents as described above can alternatively be used,adjusting ratios to achieve 80% to 90% humidity as will be readilyapparent to those skilled in the art. The bait container is made from amaterial such as paraffin, beeswax, polyurethane foam, styrofoam andfibrous casing tubes.

Naphthalenic compounds may be used to retard extreme deterioration ofwood interceptors and to congregate termites to its immediateenvironment for purposes of monitoring the size and presence of termitepopulations, e.g., by observing termites and counting or otherwiseestimating the number of termites present by measuring the consumptionof wood interceptors. Typical monitoring strategies utilizeapproximately one bait station per 10-15 linear feet. The significantlyfaster response of termites to treated pine wood as compared tountreated pine wood results in enhanced monitoring efficacy.Additionally, these chemicals may be used alone or in combination withactive secondary toxicants used in bait matrices such as streptomycinsulfate, rifampicin, albendazole, neomycin sulfate, sorbic acid,antimycotics, benzofenyl ureas, imidacloprid, hydroximethanon, juvenilehormone mimics and used in combination with preferred wood such asmaple, sitka spruce, birch, douglas fir, red gum, yellow poplar, whitepine or yellow pine wood to extend the period of termite activity at themonitoring site.

The matrix materials of this invention, may be encased in materials orcontainers which are water-retentive such that they substantiallyprevent evaporation of the moisture in the food, but which arevapor-permeable to a degree sufficient to allow termites to detect odorscoming from the matrices.

EXAMPLES Example 1 NHA-sodium Salt

For bait matrices with a final concentrations of NHA sodium salt ofeither 250 ppm or 500 ppm, the following procedure was used. A total of25 mg or 50 mg, respectively of the NHA sodium salt was weighed using aMettler balance. The NHA sodium salt complex was placed into a 50 mlsterile screw cap conical tube (#62.547.004; Sarstedt, Newton, N.C.) anddissolved with 40 ml nutritive solution described in Example 2 of U.S.patent application Ser. No. 09/294,499 filed Apr. 20, 1999, herebyincorporated by reference. Under a laminar flow hood, this product wasmixed with 27 ml more of sterile nutritional supplement in a 250 mlsterile glass bottle (prepared as reported by M. G. Rojas and J. A.Morales-Ramos, April 2001, “Bait matrix for delivery of chitin synthesisinhibitors to the Formosan subterranean termite [Isoptera:Rhinotermitidae],” J. Econ. Entomol. 94(2) :506-510) hereby incorporatedby reference. The bottle was tightly closed with a screw cap andmanually shaken for 2 minutes. The mixture was added to 33 g of sterilecellulose as reported by Rojas and Morales-Ramos (2001) supra. Themixture was manually homogenized using a stainless steel spatula. Toencase the bait matrix, tubes made of fibrous casing material (#124B;L.E.M. Products, Inc., Miamitown, Ohio) were cut into 150 mm longportions as reported by Rojas and Morales-Ramos (2001) supra. Fiftygrams of bait matrix containing NHA sodium salt was compacted into oneend of the inlet tube, and the open end and of the inlet tube was closedwith a rubber band. The bait casing was placed inside of the foragingbox adjacent to a 10 g piece of pine wood, taking care that it waspartially covered with sand. Control bait matrix was prepared minus NHA,and presented in the same way as the treatment matrix to Formosantermites taken from three different colonies, with two boxes perlocality totaling six boxes of 2500 termites per treatment. (Rojas andMorales-Ramos [2001] supra). All the experimental boxes were maintainedunder dark conditions at 27±1° C., and 90±2% relative humidity.Observations were done every 72 hours until all the termites died. Thetime to reach 100% mortality was measured and recorded. Mean comparisonsamong treatments and control were conducted.

TABLE 1 Colonies of 2500 termite workers alive after 1, 2 and 2½ monthsof feeding on non repellent lethal concentrations of NHA sodium 1 Month2 Months 2½ Months NHA-sodium salt^(a) Colonies Alive Colonies AliveColonies Alive 0 (Control) 6 6 6 250 4 3 0 500 3 1 0 ^(a)Concentrationin parts per million.

Table 1 shows that all termites in the experimental colony containingNHA were dead in about 2½ months while the termites in the control boxeswere still alive after 6 months. The cuticle of the dead termites fromthe treatment boxes had a yellowish color with a rubbery consistency. Ata concentration of NHA >500 ppm, the acceptability of the bait isreduced, since some termite colonies required more than 8 hours to startfeeding on it. This chemical agent acts very strongly against thetermites, producing a mortality of a 2,500-worker colony in about 3weeks, depending on the health and age of the colony. At NHAconcentrations above 10,000 ppm, the bait becomes unpalatable andconsumption is almost non existent above 20,000 ppm. The preferred doseis 500 mg of NHA per kilogram of bait matrix.

Example 2 N-hydroxynaphthyalimide Sodium Salt

N-hydroxynaphthyalimide (NHA) which is commercially available as purechemical, is dissolved in distilled water using a sterile container; Atconcentrations of 500 ppm, NHA is effective as bait active ingredienttaking a mean time to kill C. formosanus in 2½ months in lab conditions.Concentrations greater than 500 and up to 1500 ppm, are also effectivebut mean killing times are not significantly different.N-hydroxynaphthyalimide (NHA) sodium salt 99% (Product No. A16027, CASNo. 6207-89-2), obtained from Avocado Research Chemicals Ltd.(Massachusetts) was separately incorporated into a bait matrix (ARS baitmatrix) as described in U.S. patent application Ser. No. 09/294,499filed Apr. 20, 1999, hereby incorporated by reference. Note Example 1,above, for the creation of the NHA salt. The bait matrix was prepared byweighing 1.25 g lecithin (USB #18240), 0.450 g ergoesterol (Sigma#E-6510), 3.75 g ethyl alcohol (Quantum MT #194A31) and 650 g drinkingwater (Barbe's Dairy, West Wego, La.) into a 1 L glass bottle and mixingwell using a glass bar. The opening of the bottle was covered with afoam stopper, the bottle cap was loosely placed on top of the stopper,and the stopper covered with foil. After autoclaving for 20 minute at120° C., the bottle was closed tightly and allowed to cool down. 350 gcellulose powder (Bio-Serv #3425) was weighed into a 3 L stainless steelbowl. Polyacrylamide copolymer was weighed into a second 1 L glassbeaker, distilled water was added and the beaker was tightly coveredwith foil. After autoclaving, the bottle was closed tightly and allowedto cool. The beakers were tightly covered with foil and sterilized byautoclaving at 120° C. for 20 minutes.

Under a laminar flow hood, yeast hydrolysate (ICN Biomed. #103304) wasadded to the lecithin-containing mixture using a sterile spatula and themixture was shaken until the yeast hydrolysate was incorporated. Thebottle was tightly closed.

Using a sterile spatula, the lecithin-containing mixture was added tothe cellulose and mixed well. Finally, the polyacrylamide copolymer wasadded to the mixture and homogenized. The beaker was covered with foiland plastic to avoid contamination and loss of water. The mixture wascompacted and divided into pieces of about 25-125 g each atconcentrations of 50, 250, and 500 ppm respectively. The bioassay wasrun using the protocol of Example 1. Preliminary results testing a doserange of NHA sodium salt from 50, 250, and 500 ppm had shown that 500ppm was sufficient to induce formosan termite mortality within about twomonths without any signs of repellence to the termites. Repellence wasobserved at NHA sodium salt doses higher than 1500 ppm.

Example 3 Field Evaluation

Underground Exterra bait stations (Ensystex, Fayetteville, N.C.) wereplaced according to manufacturer directions around 20 houses in aheavily Reticulitermes spp. infested neighborhood surrounded by mainlypine forest in Past Christian, Miss. The stations were placed,approximately 20 feet apart and 5 feet away from the outside wall of thehouse. Monthly inspections were conducted to determine termite activity.Once termites were found in the station, 150 g of the ARS bait matrix(see Example 2) containing 250 ppm NHA was placed in the station for thefirst year of the experiment. The dose was increased in the second yearto 500 ppm because of the constant movement of termites from the forestarea to the stations. The bait matrix-NHA was prepared as above andexposed to the termites contained in the Exterra bait station,consecutively monthly inspections were conducted and bait matrix-NHA wasadded as required. Data on bait consumption, temperature of the soil andtime to kill the colony was recorded. Reticulitermes flavipes were veryabundant in the study site. The distribution of the infestation was inpatches. For the typical infested house, termites were found in 3 of 6stations. For this type of environmental setting, 600 g of bait matrixwhich is equivalent to 240 mg of NHA was required to kill the colony. Ittook about 9 months (from September-May) for the bait matrix to show itseffectiveness which was evaluated by the presence of dead termites onthe surface of the bait matrix container and interceptors. Table 2 showstermite activity and bait consumption from different baitings done inPast Christian, Mississippi. The length of time we believe was due tothe size of the colony as well as the lack of feeding during winter inwhich termite feeding activity is greatly reduced.

TABLE 2 Termite activity and bait consumption in a field test in PastChristian, Mississippi Active Stations Bait (Cum. weight in g) DateNumber Percentage* Added Consumed** 09/26 22 95.7 2,700 0.0 10/27 1043.5 3,600 600 11/20 10 41.7 4,650 1,200 12/18 8 33.3 4,950 1,500 01/296 24.0 5,100 1,500 02/26 12 50.0 5,550 1,500 03/27 13 56.5 6,450 1,50005/01 16 55.2 7,650 3,150 05/29 11 36.7 8,400 3,750 06/26 16 50.0 9,4504,800 07/31 12 33.3 10,800 6,000 08/28 17 47.2 12,000 7,200 09/25 2152.5 13,950 7,950 11/02 18 42.9 15,900 10,800 11/27 13 28.9 17,25011,250 12/29 13 28.9 17,850 11,850 01/29 11 24.4 17,850 11,850 02/26 1533.3 18,750 12,600 *Calculated as the percent stations that are activefrom the cumulative number of stations that have been active to themonitoring day. **Calculated from fully consumed bait bags.

Example 4 NHA-sodium Salt in Wooden Interceptors

NHA as a wood preservative has been extensively studied (F. Green III,T. A. Kuster, L. Ferge, and T. L. Highley, 1997. Protection of southernpine from fungal decay and termite damage withN,N-Naphthaloylhydroxylamine. Inter. Biodeter. and Biodeg.39(2-3):103-111; D. M. Crawford and F. Green III, 1999. Protection ofsouthern pine using N,N-Naphthaloylhydroxylamine: Field tests, soft-rotcellars and aquatic bioassay leach testing. Internat. Res. Group on WoodPreserv. Doc. No: IRG/WP 99-30204). Monitoring termite activity inbaiting systems is conducted by the use of wooden interceptorsconstructed from out of aspen, southern yellow pine, white or yellowpoplar. In humid environments such as the Southeastern United States, aproblem with degradations of such interceptors by fungi frequentlyoccurs. We have noticed that low concentrations of NHA from 200 to 1000ppm is acceptable to retard fungal growth without presenting anydeleterious effect in the termites when incorporated into woodenmaterials. For bait efficacy, when the chemical is impregnated on piecesof wood the concentration that is retained varies as well as theefficacy. The interceptors are preferably pressure treated (S. T. Lebowand S. A. Halverson, 1999. Effect of prestain on the treatability ofwestern hemlock with chromated copper arsenate. Res-Note FPL-RN-0269.Madison, Wis.: USDA, Forest Service, Forest Products Laboratory 5p.)with aqueous solutions of 0.2-1000 ppm of NHA (F. Green III, et al.,1997, supra and D. M. Crawford et al., supra).

Pieces of aspen wood (20×3.5×0.5 cm) were pressure treated with NHA asdescribed above in Lebow and Halverson, supra and placed into 6underground Exterra bait stations installed next to Formosansubterranean termite infested trees in New Orleans. The stations alsocontained pieces of untreated aspen wood as control. Inspections weredone biweekly and pieces damaged by termites were replaced. After fieldtesting 75 to 1000 ppm is acceptable and 500 ppm being the optimal. Whenapplied on wood instead of the matrix, the NHA dose varies with theimpregnation properties of each wood species.

Example 5 Copper Naphthenate Laboratory Study

Copper naphthenate (Product No. PS-2028, Chem Service, West Chester,Pa.) was dissolved in 90% warm ethanol at 3 different concentrations of50, 100 and 200 ppm. The ethanol solution was mixed with the liquid partof the ARS bait matrix (see Example 2) and bait was prepared andpresented to the termites as above in Example 1 having 4 repetitions perdose and a control. It was observed that at 50 ppm of chemical, alltermites in 50% of the boxes died at about 8 weeks; and termites in 75%of the boxes died at about 10 weeks; at 100 ppm all termites died in theboxes at 8 weeks, and at 200 ppm all termites died in all tested boxesat 8 weeks. All termites in the treatments were dead by week 12. A greatvariability in acceptance of the bait and time to kill was observed atthe 200 ppm dose. The results are reported in Table 3.

TABLE 3 Percent colonies of 2500 termite workers alive after 8, 10, and12 weeks of feeding on non repellent lethal concentrations of coppernaphthenate Time After Treatment (wks) Copper naphthenate^(a) 8 10 12 0(Control) 100 100 100 50 50 25 0 100 0 0 0 200 0 0 0 ^(a)Concentrationin parts per million.

It is understood that the foregoing detailed description is given merelyby way of illustration and that modifications and variations may be madetherein without departing from the spirit and scope of the invention.For example, choice of specific components and their relativeproportions in the matrices or wood material may readily be determinedby those skilled in the art without undue experimentation using theteachings hereof.

What is claimed is:
 1. A termite bait matrix comprising: a) cellulose;b) water; and c) one or more naphthalenic compounds selected from thegroup consisting of N-hydroxynaphthalimide and sodium, magnesium,potassium and calcium salts thereof, 1,8-napthalimide, coppernaphthenate and zinc naphthenate in amounts sufficient in termitematrices to kill termites ranging from about 10 ppm to about 500 ppm. 2.The termite bait matrix of claim 1 further comprising a water-retentionagent.
 3. The termite bait matrix of claim 2 wherein the water-retentionagent is in an amount up to about 0.05 g/kg.
 4. The termite bait matrixof claim 1 further comprising a termite toxicant.
 5. The termite matrixof claim 4 wherein said termite toxicant is selected from the groupconsisting of: streptomycin sulfate, rifampicin, albendazole, neomycinsulfate, sorbic acid, antimycotics, benzofenyl ureas, imidacloprid,hydroximethanon, juvenile hormone mimics.
 6. The termite bait matrix ofclaim 1 contained within a termite-accessible container or coating.
 7. Amethod of killing termites comprising: a) placing the termite baitmatrix of claim 1 in a termite habitat; and b) allowing termites to feedon said bait matrix.
 8. A method of monitoring termite activity in aregion comprising: a) placing the termite bait matrix of claim 1 in saidregion; and b) assessing the presence of termites at the site of saidtermite bait matrix.
 9. The method of claim 8 wherein said termite baitmatrix further comprises a water-retention agent.
 10. The method ofclaim 9 wherein said termite bait matrix is contained within awater-retentive, vapor-permeable coating or container.
 11. The termitebait matrix of claim 1 wherein the one or more naphthalenic compoundsselected from the group consisting of N-hydroxynaphthalimide and sodium,magnesium, potassium and calcium salts thereof, 1,8-napthalimide, coppernaphthenate and zinc naphthenate in amounts ranging from about 10 ppm toabout 500 ppm.